A CASE OF UNHINDERED GROWTH OF THE INCISOR 

 TEETH OF THE WOODCHUCK. 



STEPHEN R. WILLIAMS 

 Department of Zoology, Miami University 



Late in the fall of 1921, long after the normal woodchucks 

 had gone into retirement for the winter the groundhog whose 

 head is show^n herewith was caught near Oxford in a trap set for 

 skunks. The trapper killed the woodchuck with a club, breaking 

 two of the teeth in the process, one of which he picked up. The 

 pelt being valueless he cut off the peculiar looking head and 

 threw the body away making the observation that the animal 

 was much undersized and excessively thin. 



The head was brought in, mounted by a local taxidermist, 

 and put upon exhibition in an office window. I take this oppor- 

 tunity to thank the exhibitor, Mr. Chas. Wright, for permis- 

 sion to photograph the mount. 



There is no evidence as to what happened to deform the 

 animals, but the results are clear. In some way the incisor teeth 

 of the woodchuck's lower jaw became deflected to the animal's 

 left side and the incisors of the upper jaw turned enough to the 

 right so that the two sets passed each other and no longer could 

 be kept worn down by gnawing. 



The left lower incisor grew in a regular curve up to the eye, 

 ploughed through the eye and blinded it. It can be seen that 

 the direction of growth was changed into a section of a larger 

 circle as the end of the tooth slid backward along the frontal 

 bone. The continuous curving growth of the tooth was not to 

 be resisted by bone, however, and so the point of the tooth per- 

 forated the skull a short distance behind the eye socket and is 

 said by the preparator to have penetrated the brain also. 



This perforation of the skull and brain must have been some 

 time before the animal's death, for the last visible part of the 

 tooth is sheathed with a connective tissue envelop probably 

 continuous with the periosteum of the skull through which the 

 tooth passed. How far into the brain the tooth penetrated can 

 never be determined. The whole socket of the eye was a sup- 

 purating mass when the animal was killed. 



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